FXUS61 KCLE 010221
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1021 PM EDT Wed Apr 30 2025

.SYNOPSIS...
Another low pressure system is headed for the southern Great
Lakes tonight with a warm front pushing through, followed by a
cold front Thursday and more thunderstorm potential. An upper
level cutoff low with cooler weather moves in for the weekend.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
10:15 PM Update:
No notable changes to the forecast through Thursday. Massaged
the timing of higher shower/storm chances a bit in the grids.

Showers falling out of a mid-level deck produced a few sprinkles
at the ground in Northwest OH this evening, though are now
shifting east over Lake Erie. Scattered showers, and perhaps an
elevated storm or two, will arc northeast across the area just
ahead of a warm front overnight tonight into early Thursday. We
will then get into the open warm sector on Thursday, and should
see a few hours of mainly dry weather (outside of a lingering
isolated shower or two) with at least breaks of sun.

The main focus Thursday afternoon and early evening then shifts
to potential for convection to develop along/ahead of a cold
front approaching from the west. Most regional and hi-res models
suggest a pre-frontal trough or two progressing east across our
area through the afternoon and early evening, and these are
expected to be the primary foci for convective development in
the afternoon. The cold front pushes in from the west Thursday
evening, with a weakening line of convection potentially
accompanying it. Some disagreement regarding the amount of
heating along with the placement for those more subtle pre-
frontal troughs leads to uncertainty regarding the specifics
regarding the convective evolution and severe threat. However,
despite somewhat limited heating and poor mid-level lapse rates,
it seems that 750-1500 J/KG of MLCAPE should develop during the
afternoon in a moderately sheared (35-45kt of deep-layer shear)
environment. This does support organized convection with some
severe threat if we see any supercells early in the convective
cycle (most likely from far eastern OH into PA where low-level
flow may remain more backed into the afternoon), or if we see
upscale growth into lines or clusters...with enough 0-3km shear
to support an embedded bow or two with any upscale growing
clusters. While uncertainty remains, stay tuned for updates.

Previous Discussion:
The active pattern will continue despite a day of drying with cooler
air and low dewpoints. Warm front to cross the CWA border southwest
to northeast late tonight with an expected cluster of showers and
isolated thunder within. The instability above a steep surface
inversion is not favorable for thunder but cannot eliminate the
potential based on forced ascent as there will exist very modest
CAPE around 700mb. The surface low of this low pressure system will
track also from southwest to northeast from central Illinois towards
Lake Huron, west of our CWA boundary. Will be in the warm sector for
a short period of time early Thursday into the afternoon/evening
hours. Small areas of PVA within the southwest 500mb flow/height
gradient will necessitate the need for low end POPs while in the
warm sector residence time. Main line of convection is going to form
ahead of the cold front with main initiation time of after 16Z. Far
western zones may not see this activity as the progress of the cold
front may be through that area before cells/line develops. As far as
the severe potential goes, there could be a concern with the
antecedent cloud cover and showers working to inhibit strength
through CAPE, but the convection itself will not rely on
thermodynamics to get going and should have enough shear to organize
it. Expecting gusty winds and cannot eliminate a hail threat, but
with the surface winds veering ahead of the front the tornado risk
decreases, but again, non-zero. In the end, the severe threat is
highest for the eastern two-thirds of the CWA.

The yo yo-ing of temperatures continues, and after a day highly
influenced by the ENE winds off Lake Erie and temperatures in the
upper 40s to mid 50s, with 60s in the southern CWA, upper 70s to
around 80F is possible in the warm sector prior to the line of
convection/cold front.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Aloft, SW'erly cyclonic flow and embedded/subtle shortwave
disturbances affect our region through Saturday as a prominent
trough axis shifts SE'ward from the northwestern Great Lakes and
central Great Plains to near Lake Huron and the Lower OH Valley,
when an embedded mid/upper-level low should develop near the IL/IN
border area. At the surface, a front should waver just west and
north of Lake Erie through Friday afternoon as one frontal low moves
ENE'ward across southeastern ON, north of Lake Ontario, and southern
QC, and a separate frontal low moves from the southwestern Great
Lakes toward southern Lake Huron. The front should sweep SE'ward as
a cold front across Lake Erie and our CWA Friday evening through
Friday night as the second aforementioned frontal low moves farther
ENE'ward toward the Upper Saint Lawrence River Valley. Behind the
cold front, a trough is expected to linger over the Lake Erie region
and Upper OH Valley.

Peeks of sunshine and low-level warm/moist air advection from the
Gulf are expected to allow late afternoon highs to reach the 60's to
lower 70's on Friday. Low-level CAA behind the cold front should
contribute to Friday night's lows reaching the upper 40's to lower
50's around daybreak Saturday. Despite peeks of sunshine on
Saturday, continued low-level CAA is expected to limit late
afternoon highs to the mid 50's to lower 60's in our CWA.

Scattered showers and thunderstorms should occur along and ahead of
the cold front Friday into Friday night as low-level
convergence/moist ascent along the front and surface trough axes
accompanying the aforementioned shortwave disturbances release
surface-based and elevated CAPE, and moist isentropic ascent ahead
of the shortwave trough axes releases elevated CAPE. Instability is
expected to be mainly weak, but limited daytime heating of the
warm/moist sector boundary layer may yield moderate surface-based
CAPE Friday afternoon through early evening. Showers/storms should
produce periods of heavy rain amidst unusually-high PWAT values in
the warm/moist sector. Some storms may be strong to severe amidst
moderate to strong deep-layer bulk shear. SW'erly mean mid-level
flow around 40 to 50 knots is expected to allow showers/storms to
train along the front, but fast shower/storm motions should limit
flash flood potential. Behind the front, additional and scattered
rain showers are expected Friday night through Saturday courtesy of
moist isentropic ascent ahead of the prominent trough axis aloft.

During Saturday night, SW'erly flow aloft, over our CWA, should back
to S'erly to SE'erly as the trough aloft settles SE'ward over our
region and the embedded mid/upper-level low drifts SE'ward from near
the IL/IN border area toward the Mid OH Valley. Scattered rain
showers should continue to impact our region as the low pressure
system's warm conveyor belt undergoes moist isentropic ascent aloft.
At the surface, a trough should linger over/near our CWA. Lows
should reach the 40's around daybreak Sunday as low-level CAA
persists across our region.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The latest consensus of NWP model guidance indicates troughing at
the surface and aloft should continue to impact the Lake Erie region
and Upper OH Valley during the long-term period. Simultaneously, the
mid/upper-level low mentioned in the short-term forecast discussion
should wobble near the Mid OH Valley through Tuesday before moving
ENE'ward toward NJ and vicinity on Wednesday as a downstream
blocking ridge aloft over the northwestern Atlantic begins to
weaken. Periodic and scattered rain showers are expected on Sunday
through Wednesday, respectively, due to the following: the low
pressure system's warm conveyor belt undergoing moist isentropic
ascent aloft; low-level convergence/moist ascent along surface
trough axes expected to accompany shortwave disturbances that should
revolve around the mid/upper-level low. The best potential for
showers should exist each late morning through early evening due to
the expectation of a typical diurnal cycle in surface air
temperatures/boundary layer stability (e.g. weak diurnal
destabilization of a moist boundary layer). The low-level
convergence/moist ascent along the aforementioned surface trough
axes may release sufficient boundary layer CAPE to trigger a few
late afternoon and early evening thunderstorms, especially on Monday
through Wednesday, respectively.

A gradual moderating trend in surface air temperatures is expected
during the long-term period as low-level temperature advection
amidst the slow-moving low pressure system's cyclonic circulation
eventually allows relatively-warmer air to overspread our region
from the north and west as north-south baroclinicity decreases and
cloud cover decreases gradually. Late afternoon highs in the mid
50's to mid 60's on Sunday and the 60's to lower 70's on Monday
should moderate to late afternoon highs reaching the mid 60's to mid
70's on Tuesday and Wednesday, respectively. Lows should reach the
lower 40's to lower 50's around daybreak Monday and Tuesday,
respectively, and the upper 40's to mid 50's around daybreak
Wednesday.

&&

.AVIATION /00Z Thursday THROUGH Monday/...
VFR is observed across the board this evening. A deck of mid-
level clouds is producing some showers across Northwest OH...
these are mainly not reaching the ground so only included VCSH
at TOL. A warm front lifts northeast across the area overnight
tonight and early Thursday. Scattered showers will likely
accompany this feature. Any restrictions would be brief, though
there will be some elevated instability so an isolated heavier
shower or storm is possible. Generally handled with VCSH
mentions, with some PROB30 groups for brief reduced visibility
and/or TS where potential for this appears higher. We get into
the warm sector ahead of an approaching cold front Thursday
morning and early afternoon. This cold front begins pushing in
from the west towards Thursday evening. While isolated shower
potential can't be ruled out in the open warm sector, a few
hours of mainly dry weather with some breaks in the clouds is
likely. Storm potential ramps up ahead of the cold front through
the afternoon and early evening on Thursday. Confidence in
impacts is rather high from CLE-MFD points east, though
confidence is a bit lower at TOL and FDY. Thunderstorms in the
afternoon will be capable of brief vsby and ceiling
restrictions, along with gusty winds locally to 40kt or more.
Storms will generally move to the northeast at ~40kt.

Winds will be light out of the east to southeast tonight. Winds
shift south-southwest into Thursday and increase to 12-20kt
sustained with gusts 25-30kt common by the afternoon.

Outlook...Non-VFR potential with showers/storms lingers into
Thursday night. Non-VFR may linger across the eastern half of
the area into Saturday.

&&

.MARINE...
Onshore winds around 5 to 10 knots, associated with a lake breeze
through this early evening, give way to NE'erly to SE'erly winds
around 5 to 15 knots tonight as a ridge begins to exit toward New
England. Waves of 3 feet or less are expected. On Thursday through
Friday night, a low should move NE'ward from the Mid MS Valley
toward the mouth of the Saint Lawrence River. Accordingly, a warm
front should drift N'ward across Lake Erie on Thursday and allow
NE'erly to SE'erly winds around 10 to nearly 20 knots to veer to
S'erly to SW'erly. Waves remain mainly 3 feet or less in U.S.
waters, but occasional 4 footers are expected in open U.S. waters.
Behind the warm front, SW'erly winds around 10 to 15 knots persist
before a cold front sweeps SE'ward across Lake Erie Friday evening
through Friday night and causes winds around 10 to 15 knots to veer
to NW'erly. Waves of mainly 3 feet or less should persist, but
occasional 4 footers are possible. We will monitor forecast trends
for the potential need for a Small Craft Advisory.

Behind the cold front, a trough should linger over Lake Erie through
this weekend and Monday as a ridge attempts to build from the north-
central United States. NW'erly winds around 10 to 15 knots should
veer gradually to E'erly. Waves of 3 feet or less are forecast.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.

&&

$$

SYNOPSIS...26
NEAR TERM...26/Sullivan
SHORT TERM...Jaszka
LONG TERM...Jaszka
AVIATION...Sullivan
MARINE...Jaszka